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Biomedical subjects

H Tokuno

Publications and source records attributed to H Tokuno.

86 records · Page 5Linked to original sources
PubMed1988

Effects of nifedipine on intracranial pressure in neurosurgical patients with arterial hypertension.

The effects of nifedipine, 20 mg administered via a nasogastric tube, on intracranial pressure (ICP) and cerebral perfusion pressure (CPP) were examined. Nifedipine was administered to treat arterial hypertension (greater than 180 mm Hg, systolic). Ten measurements were made in eight patients with cerebrovascular disease or head trauma. The mean arterial blood pressure (MABP) and ICP were measured before and for 30 minutes after the administration of nifedipine. The MABP gradually decreased and reached its lowest value at approximately 10 minutes after initiation of nifedipine administration, and thereafter remained unchanged. The MABP decreased significantly from 128 +/- 8 (mean +/- standard deviation) to 109 +/- 7 mm Hg, and the CPP decreased from 105 +/- 11 to 84 +/- 10 mm Hg. The ICP increased by 1 to 10 mm Hg in eight of 10 measurements, and the mean change of ICP from 19 +/- 7 to 22 +/- 6 mm Hg was statistically significant. These changes were not accompanied by alterations in neurological signs. The results suggest that enteral nifedipine produces a small but statistically significant increase in ICP. Accordingly, neurological signs must be closely observed to detect deterioration, which can be caused by an increase in ICP and/or a decrease in CPP.

Adult↗
PubMed1987

Organization of the nigrotectospinal pathway in the cat: a light and electron microscopic study.

The relationships between nigrotectal terminals and tectospinal neurons in the deep layers of the superior colliculus have been examined light and electron microscopically by using antero- and retrograde transport of tracer, and anterograde degeneration. For light microscopy, horseradish peroxidase (HRP) was injected into the cervical spinal cord, and HRP conjugated to wheat germ agglutinin (WGA-HRP) into the substantia nigra at the same time. It appeared that about 22% of the retrogradely labeled tectospinal neurons were totally or partially in the anterogradely labeled nigral terminal clusters. This coexistence was particularly manifest in the dorso-lateral part of the intermediate gray layer. For electron microscopy, nigral lesions and HRP injections into the cervical spinal cord were combined in the same animals. Degenerating nigrotectal terminals were found in both axosomatic and axodendritic symmetrical synaptic contacts with retrogradely labeled tectospinal neurons in the intermediate gray layer. Present experiments show tectospinal neurons receiving monosynaptic input from the substantia nigra do exist in the intermediate gray layer of the superior colliculus, especially in its dorsolateral portion.

Animals↗
PubMed1987

Collagenase eliminates the electrical responses of smooth muscle to catecholamines.

The effects of collagenase on the membrane response to catecholamines were studied with intracellular microelectrodes in the guinea-pig taenia caeci and main pulmonary artery. In the taenia, the inhibitory actions of adrenaline mediated through alpha- and beta-adrenoceptors were both nearly abolished by two 5-min treatments with 0.005% collagenase. In the pulmonary artery, the depolarizing action of noradrenaline mediated through beta-adrenoceptors was markedly reduced by three 5-min treatments with 0.01% collagenase.

Animals↗
PubMed1985

Possibility of metabolic control of membrane excitation.

In the guinea pig taenia coli, when glycogen is depleted by repeating Ca-induced contracture in excess K solution containing no glucose, the tension cannot be maintained. The decrease in tension is accompanied by reduction of high energy phosphate compounds and oxygen consumption. When substrate is readmitted to the glycogen-depleted preparation in the presence of 2.4 mM Ca and 20 mM K, the first response is hyperpolarization of the membrane and relaxation, and this is followed by depolarization and development of contracture. The latter response is blocked by verapamil, suggesting that energy supply increases the Ca conductance of the plasma membrane. The early response is considered to be due to activation of electrogenic Ca pump, since this is not affected by ouabain as well as removal of Na and K. ATP produced by substrate readmission is probably preferentially utilized for Ca pump activation to reduce the intracellular Ca. The recovery of tension is likely to be brought about by ATP supply not only to the contractile machinery but also to the plasma membrane to remove inactivation of Ca conductance. It is postulated that as the energy source is depleted, energy consumption is automatically limited by suppressing Ca influx, as a self-defence mechanism. Since beta HB is as effective as glucose in the recovery of these processes, and also in the activation of electrogenic Na pump, the metabolic pathway of oxidative phosphorylation alone can support these functions without a contribution of the glycolytic pathway.

Animals↗
PubMed1985

Effects of readmission of substrate on the membrane potential in glycogen-depleted guinea-pig taenia coli.

In the glycogen-depleted smooth muscle of the guinea-pig taenia coli, application of glucose or beta-hydroxybutyrate (beta-HB) in the presence of 20 mM-K or carbachol (5 microM) produced a transient hyperpolarization for about 1 min followed by a sustained depolarization accompanied by spike activity. The early hyperpolarization was highly temperature dependent, so that below 30 degrees C, substrate application produced the depolarization with a delay of approximately 2 min, without a clear preceding hyperpolarization. The responses to substrate were not affected by ouabain (10 microM). Readmission of K after a treatment with K-free solution for 10 min caused a transient hyperpolarization only in the presence of substrate. This hyperpolarization was abolished by ouabain. Verapamil (0.1 microM) blocked the substrate-induced depolarization, revealing an underlying slow hyperpolarization. Removal of Ca abolished both the hyperpolarization and depolarization caused by substrate application, but the hyperpolarization disappeared much more slowly than the depolarization. Removal of the external K had little effect on the substrate-induced hyperpolarization, but the hyperpolarization induced by substrate application was increased when the external K was increased up to approximately 20 mM. Both the hyperpolarization and the depolarization were not clearly affected by completely replacing Na with choline. The results suggest that ATP supplied by the addition of substrate activates some electrogenic pump, probably a Ca pump, causing hyperpolarization, and that ATP also removes the inactivation of Ca conductance with some delay, resulting in an increased depolarization.

3-Hydroxybutyric Acid↗
PubMed1984

Enterotoxigenicity of Staphylococcus intermedius strains isolated from dogs.

Dogs (n = 100) were examined for the presence of enterotoxigenic Staphylococcus intermedius. Enterotoxigenic strains were isolated from the nasal cavities of 43 (43.0%) out of 100 dogs. Of the 50 enterotoxigenic strains isolated, 23 (46.0%) produced enterotoxin A, 17 (34.0%) enterotoxins A and C, 8 (16.0%) enterotoxin C, and only two (4.0%) enterotoxins A and B. The amount of enterotoxin produced on semisolid brain heart infusion medium by the 17 enterotoxin A producing strains of S. intermedius was 10-160 ng per ml. Enterotoxin A production by S. intermedius strains was ony one tenth to one hundredth of that of S. aureus strains from staphylococcal food poisoning outbreaks.

Animals↗
PubMed1984

Effects of glucose removal and readmission on potassium contracture in the guinea-pig taenia coli.

The effects of removal and readmission of substrates on the K contracture were investigated in the guinea-pig taenia coli. When, after exposure to excess K in Ca-free and glucose-free medium, the readmission and removal of 2.4 mM-Ca were repeated at regular intervals, the Ca-induced contractions decreased progressively. The decrease was more marked in the late than in the early part of the tension response. The rate of O2 consumption decreased when the normal medium was replaced by glucose-free, Ca-free, excess-K solution, but substantially recovered following Ca readmission. ATP and creatine phosphate contents decreased during the Ca-induced contraction, but recovered partially during the subsequent relaxation in Ca-free solution. The effects of glucose removal were rapidly reversed when glucose or beta-hydroxybutyrate (beta-HB) were readmitted to the bathing solution. In the absence of Ca, readmission and removal of the substrates produced an insignificant change in O2 consumption, but the next Ca contraction was potentiated, the effect being stronger with glucose than beta-HB. When the tonic contraction evoked by 2.4 mM-Ca readmission had been abolished in glucose-free, high-K solution, a rise of the external Ca concentration to 10 mM, or 5 microM-carbachol, still produced a transient contraction. This suggests that the tonic contraction has disappeared partially because of diminished Ca influx. In glycogen-depleted preparations, the depolarization caused by carbachol, or by 20 mM-K, was increased and spike discharge initiated when glucose was readmitted.(ABSTRACT TRUNCATED AT 250 WORDS)

3-Hydroxybutyric Acid↗
PubMed1976

Impedance components in longitudinal direction in the guinea-pig taenia coli.

1. When the tissue impedance of the guinea-pig taenia coli was measured across a 2 mm sucrose gap in a longitudinal direction, the impedance locus could be fitted by two different circular arcs. Their characteristic frequencies were about 0-6 and 240 Hz after 60 min superfusion with sucrose solution. From the effects of changing the width of sucrose gap and of transection of tissue, and also from taking the difference between impedances measured at two distances, it was concluded that the low-frequency locus corresponds to the transverse impedance of the plasma membrane and the high-frequency locus to the longitudinal tissue impedance. 2. A change in the longitudinal tissue impedance was measured during superfusion with sucrose solution, using a frequency range between 5 Hz and 10 kHz. The admittance decreased with time of superfusion and this time course could be expressed by the sum of three exponential terms. The fastest component, having a time constant of 1-3 min at 10 kHz, was interpreted to correspond to a process of wash-out of extracellular medium. 3. Admittances at zero and infinite frequencies were obtained from the impedance locus. The decrease in these admittances with the time was analysed and the values at the start of washing were obtained by extrapolating the admittance change to zero time. 4. From these values it was estimated that the myoplasmic resistance was 214 omega cm, the junctional resistance 372 omega cm, and the junctional capacity 3-1 muF/cm at 25 degrees C. In these calculations the equivalent circuit of tissue was assumed to be expressed by two components in series: one for the myoplasmic resistance and the other for the junction which has the junctional resistance and capacity in parallel. 5. After 90 min superfusion with sucrose solution, the total tissue impedance measured at zero frequency was increased from 586 to 3034 omega cm. In the total impedance the myoplasmic resistance was increased from 214 to 914 omega cm and the junctional resistance from 372 to 2120 omega cm. Thus, the change in junctional resistance was greater than that in myoplasmic resistance during superfusion of sucrose solution.

Animals↗